@article{KrahfussRadius2021,
  author    = {Krahfuss, Mirjam J. and Radius, Udo},
  title     = {N-Heterocyclic Silylene Main Group Element Chemistry: Adduct Formation, Insertion into E-X Bonds and Cyclization of Organoazides},
  series = {European Journal of Inorganic Chemistry},
  volume    = {2021},
  journal   = {European Journal of Inorganic Chemistry},
  number    = {6},
  doi       = {10.1002/ejic.202000942},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224507},
  pages     = {548 -- 561},
  year      = {2021},
  abstract  = {Investigations concerning the reactivity of the N-heterocyclic silylene Dipp\(_{2}\)NHSi (1, 1,3-bis(2,6-diisopropylphenyl)-1,3-diaza-2-silacyclopent-4-en-2-ylidene) towards selected alanes and boranes, elemental halides X\(_{2}\) (X=Br, I), selected halide containing substrates such as tin chlorides and halocarbons, as well as organoazides are presented. The NHSi adducts Dipp\(_{2}\)NHSi⋅AlI\(_{3}\) (2), Dipp\(_{2}\)NHSi⋅Al(C\(_{6}\)F\(_{5}\))\(_{3}\) (3), and Dipp\(_{2}\)NHSi⋅B(C\(_{6}\)F\(_{5}\))\(_{3}\) (4) were formed by the reaction of Dipp\(_{2}\)NHSi with the corresponding Lewis acids AlI\(_{3}\), Al(C\(_{6}\)F\(_{6}\))\(_{3}\) and B(C\(_{6}\)F\(_{5}\))\(_{3}\). Adducts 3 and 4 were tested with respect to their ability to activate small organic molecules, but no frustrated Lewis pair reactivity was observed. Reactions of Dipp\(_{2}\)NHSi with Br\(_{2}\), I\(_{2}\), Ph\(_{2}\)SnCl\(_{2}\) and Me\(_{3}\)SnCl led to formation of Dipp\(_{2}\)NHSiBr\(_{2}\) (5), Dipp\(_{2}\)NHSiI\(_{2}\) (6), Dipp\(_{2}\)NHSiCl\(_{2}\) (7) and {(Me\(_{3}\)Sn)N(Dipp)CH}\(_{2}\) (8), respectively. The reaction with the halocarbons methyl iodide, benzyl chloride, and benzyl bromide afforded the insertion products Dipp\(_{2}\)NHSi(I)(CH\(_{3}\)) (9), Dipp\(_{2}\)NHSi(Cl)(CH\(_{2}\)Ph) (10) and Dipp\(_{2}\)NHSi(Br)(CH\(_{2}\)Ph) (11). Reaction of Dipp\(_{2}\)NHSi with the organoazides Ad-N\(_{3}\) (Ad=adamantyl) and TMS-N\(_{3}\) (TMS=trimethylsilyl) led to the formation of 1-Dipp\(_{2}\)NHSi-2,5-bis(adamantyl)-tetrazoline (12) and bis(trimethylsilyl)amido azido silane (13), respectively. For 2,6-(diphenyl)phenyl-N\(_{3}\) C-H activation occurs and a cyclosilamine 14 was isolated.},
  language  = {en}
}
@article{SundermeyerRadiusBurschka1992,
  author    = {Sundermeyer, Joerg and Radius, Udo and Burschka, Christian},
  title     = {Organometall-Imide - h{\"o}hervalente Derivate der d-Metall-S{\"a}uren, 3. Synthese ond Reaktionen von (Pentamethylcyclopentadienyl)(imido)-Komplexen des Molybd{\"a}ns und Wolframs und eine effiziente Strategie zur Synthese der Organometallate NBu\(_4\)[Cp*MO\(_3\)] (M = Mo, W)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31884},
  year      = {1992},
  abstract  = {A convenient and new entry into the chemistry of highvalent pentamethylcyclopentadienyl halfsandwich complexes of molybdenum and tungsten is described. The reaction of Mo-(NtBu)\(_2\)Cl\(_2\) or W(NtBu)\(_2\)Cl\(_2\)(py)\(_2\) with Cp*Li (Cp* = \(\eta^5\)-C\(_5\)Me\(_5\)) provides a high-yield route to new complexes Cp*Mo-(NtBu)\(_2\)CI (la) and Cp*W(NtBu)\(_2\)Cl (1 b) which are converted into a variety of diimido, monoimido, and oxo derivatives. Treatment of 1 a, b with MeLi yields the highly volatile methyl derivatives Cp*Mo(NtBu)\(_2\)Me (2a) and Cp*W(NtBu)\(_2\)Me (2b), while protolysis of 1 a, b with an excess of HCI gas leads to selective cleavage of only one imido function with formation of Cp*Mo(NtBu)Cl\(_3\) (3a) and Cp*W(NtBu)Cl\(_3\) (3b). In contrast, protolysis of 1 a, b with aqueous HCI provides a high-yield route to the well-known organometallic oxides [Cp*MoO\(_2\)](μ-0) (4a) and [Cp*WO\(_2\)](\(\mu\)-0) (4b). These two key compounds are easily converted into the organomolybdate and organotungstate salts NBu\(_4\)[Cp*MoO\(_3\)] (5a) and NBu\(_4\)[Cp*WO\(_3\)] (Sb) by cleavage of the M - 0 - M bridge with NBu\(_4\)[OH]. The Xray structure of 3a is reported.},
  subject      = {Pentamethylcyclopentadienderivate},
  language  = {de}
}
@article{LiuMingLuoetal.2020,
  author    = {Liu, Xiaocui and Ming, Wenbo and Luo, Xiaoling and Friedrich, Alexandra and Maier, Jan and Radius, Udo and Santos, Webster L. and Marder, Todd B.},
  title     = {Regio- and Stereoselective Synthesis of 1,1-Diborylalkenes via Br{\o}nsted Base-Catalyzed Mixed Diboration of Alkynyl Esters and Amides with BpinBdan},
  series = {European Journal of Organic Chemistry},
  volume    = {2020},
  journal   = {European Journal of Organic Chemistry},
  number    = {13},
  doi       = {10.1002/ejoc.202000128},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214728},
  pages     = {1941 -- 1946},
  year      = {2020},
  abstract  = {The NaOtBu-catalyzed mixed 1,1-diboration of terminal alkynes using the unsymmetrical diboron reagent BpinBdan (pin = pinacolato; dan = 1,8-diaminonaphthalene) proceeds in a regio- and stereoselective fashion affording moderate to high yields of 1,1-diborylalkenes bearing orthogonal boron protecting groups. It is applicable to gram-scale synthesis without loss of yield or selectivity. The mixed 1,1-diborylalkene products can be utilized in Suzuki-Miyaura cross-coupling reactions which take place selectivly at the C-B site. DFT calculations suggest the NaOtBu-catalyzed mixed 1,1-diboration of alkynes occurs through deprotonation of the terminal alkyne, stepwise addition of BpinBdan to the terminal carbon followed by protonation with tBuOH. Experimentally observed selective formation of (Z)-diborylalkenes is supported by our theoretical studies.},
  language  = {en}
}
@article{HuangHuShietal.2022,
  author    = {Huang, Mingming and Hu, Jiefeng and Shi, Shasha and Friedrich, Alexandra and Krebs, Johannes and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.},
  title     = {Selective, Transition Metal-free 1,2-Diboration of Alkyl Halides, Tosylates, and Alcohols},
  series = {Chemistry-A European Journal},
  volume    = {28},
  journal   = {Chemistry-A European Journal},
  number    = {24},
  doi       = {10.1002/chem.202200480},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318262},
  year      = {2022},
  abstract  = {Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional molecules represents an extremely useful process in organic synthesis. Herein, we describe a transition metal-free, simple and efficient strategy to access alkyl 1,2-bis(boronate esters) via regio- and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcohols. Control experiments demonstrated that the key to this high reactivity and selectivity is the addition of a combination of potassium iodide and N,N-dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late-stage modification of complex molecules. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be especially useful in a lead optimization program.},
  language  = {en}
}
@article{LiuKoleBudimanetal.2021,
  author    = {Liu, Zhiqiang and Kole, Goutam Kumar and Budiman, Yudha P. and Tian, Ya-Ming and Friedrich, Alexandra and Luo, Xiaoling and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.},
  title     = {Transition metal catalyst-free, base-promoted 1,2-additions of polyfluorophenylboronates to aldehydes and ketones},
  series = {Angewandte Chemie International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie International Edition},
  number    = {30},
  doi       = {10.1002/anie.202103686},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256487},
  pages     = {16529-16538},
  year      = {2021},
  abstract  = {A novel protocol for the transition metal-free 1,2-addition of polyfluoroaryl boronate esters to aldehydes and ketones is reported, which provides secondary alcohols, tertiary alcohols, and ketones. Control experiments and DFT calculations indicate that both the ortho-F substituents on the polyfluorophenyl boronates and the counterion K\(^+\) in the carbonate base are critical. The distinguishing features of this procedure include the employment of commercially available starting materials and the broad scope of the reaction with a wide variety of carbonyl compounds giving moderate to excellent yields. Intriguing structural features involving O-H⋅⋅⋅O and O-H⋅⋅⋅N hydrogen bonding, as well as arene-perfluoroarene interactions, in this series of racemic polyfluoroaryl carbinols have also been addressed.},
  language  = {en}
}
@article{JosSzwetkowskiSlebodnicketal.2022,
  author    = {Jos, Swetha and Szwetkowski, Connor and Slebodnick, Carla and Ricker, Robert and Chan, Ka Lok and Chan, Wing Chun and Radius, Udo and Lin, Zhenyang and Marder, Todd B. and Santos, Webster L.},
  title     = {Transition Metal-Free Regio- and Stereo-Selective trans Hydroboration of 1,3-Diynes: A Phosphine-Catalyzed Access to (E)-1-Boryl-1,3-Enynes},
  series = {Chemistry - A European Journal},
  volume    = {28},
  journal   = {Chemistry - A European Journal},
  number    = {63},
  doi       = {10.1002/chem.202202349},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293784},
  year      = {2022},
  abstract  = {We report a transition metal-free, regio- and stereo-selective, phosphine-catalyzed method for the trans hydroboration of 1,3-diynes with pinacolborane that affords (E)-1-boryl-1,3-enynes. The reaction proceeds with excellent selectivity for boron addition to the external carbon of the 1,3-diyne framework as unambiguously established by NMR and X-ray crystallographic studies. The reaction displays a broad substrate scope including unsymmetrical diynes to generate products in high yield (up to 95 \%). Experimental and theoretical studies suggest that phosphine attack on the alkyne is a key process in the catalytic cycle.},
  language  = {en}
}
@article{ZapfPetersBertermannetal.2022,
  author    = {Zapf, Ludwig and Peters, Sven and Bertermann, R{\"u}diger and Radius, Udo and Finze, Maik},
  title     = {Tricyanoborane-Functionalized Anionic N-Heterocyclic Carbenes: Adjustment of Charge and Stereo-Electronic Properties},
  series = {Chemistry - A European Journal},
  volume    = {28},
  journal   = {Chemistry - A European Journal},
  number    = {39},
  doi       = {10.1002/chem.202200275},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287200},
  year      = {2022},
  abstract  = {The 1-methyl-3-(tricyanoborane)imidazolin-2-ylidenate anion (2) was obtained in high yield by deprotonation of the B(CN)3-methylimidazole adduct 1. Regarding charge and stereo-electronic properties, anion 2 closes the gap between well-known neutral NHCs and the ditopic dianionic NHC, the 1,3-bis(tricyanoborane)imidazolin-2-ylidenate dianion (IIb). The influence of the number of N-bonded tricyanoborane moieties on the σ-donating and π-accepting properties of NHCs was assessed by quantum chemical calculations and verified by experimental data on 2, IIb, and 1,3-dimethylimidazolin-2-ylidene (IMe, IIa). Therefore NHC 2, which acts as a ditopic ligand via the carbene center and the cyano groups, was reacted with alkyl iodides, selenium, and [Ni(CO)\(_{4}\)] yielding alkylated imidazoles 3 and 4, the anionic selenium adduct 5, and the anionic nickel tricarbonyl complex 8, respectively. The results of this study prove that charge, number of coordination sites, buried volume (\%V\(_{bur}\)) and σ-donor and π-acceptor abilities of NHCs can be effectively fine-tuned via the number of tricyanoborane substituents.},
  language  = {en}
}
@article{FoehrenbacherZehKrahfussetal.2021,
  author    = {F{\"o}hrenbacher, Steffen A. and Zeh, Vivien and Krahfuss, Mirjam J. and Ignat'ev, Nikolai V. and Finze, Maik and Radius, Udo},
  title     = {Tris(pentafluoroethyl)difluorophosphorane and N-Heterocyclic Carbenes: Adduct Formation and Frustrated Lewis Pair Reactivity},
  series = {European Journal of Inorganic Chemistry},
  volume    = {2021},
  journal   = {European Journal of Inorganic Chemistry},
  number    = {20},
  doi       = {10.1002/ejic.202100183},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257386},
  pages     = {1941-1960},
  year      = {2021},
  abstract  = {The synthesis and characterization of Lewis acid/base adducts between tris(pentafluoroethyl)difluorophosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) and selected N-heterocyclic carbenes (NHCs) R\(_{2}\)Im (1,3-di-organyl-imidazolin-2-ylidene) and phosphines are reported. For NHCs with small alkyl substituents at nitrogen (R=Me, nPr, iPr) the adducts NHC ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) (2 a-h) were isolated. The reaction with the sterically more demanding NHCs Dipp\(_{2}\)Im (1,3-bis-(2,6-di-iso-propylphenyl)-imidazolin-2-ylidene) (1 i) and tBu\(_{2}\)Im (1,3-di-tert-butyl-imidazolin-2-ylidene) (1 j) afforded the aNHC adducts 3 i and 3 j (a denotes "abnormal" NHC coordination via a backbone carbon atom). The use of tBuMeIm (1-tert-butyl-3-methyl-imidazolin-2-ylidene) (1 m) led to partial decomposition of the NHC and formation of the salt [tBuMeIm-H][MeIm ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)] (4 m). The phosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) forms adducts with PMe\(_{3}\) but does not react with PPh\(_{3}\) or PCy\(_{3}\). The mer-cis isomer of literature-known Me\(_{3}\)P ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) (5 a) was structurally characterized. Mixtures of the phosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) and the sterically encumbered NHCs tBu\(_{2}\)Im, Dipp\(_{2}\)Im, and Dipp\(_{2}\)Im\(^{H2}\) (1,3-bis-(2,6-di-iso-propylphenyl)-imidazolidin-2-ylidene) (1 k) showed properties of FLPs (Frustrated Lewis Pairs) as these mixtures were able to open the ring of THF (tetrahydrofuran) to yield NHC-(CH\(_{2}\))\(_{4}\)O-PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) 6 i-k. Furthermore, the deprotonation of the weak C-H acids CH\(_{3}\)CN, acetone, and ethyl acetate was achieved, which led to the formation of the corresponding imidazolium salts and the phosphates [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(CH\(_{2}\)CN)]\(^{-}\) (7), [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(OC(=CH\(_{2}\))CH\(_{3}\))]\(^{-}\) (8) and [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(CH\(_{2}\)CO\(_{2}\)Et)]\(^{-}\) (9).},
  language  = {en}
}
@article{FoehrenbacherKrahfussZapfetal.2021,
  author    = {F{\"o}hrenbacher, Steffen A. and Krahfuss, Mirjam J. and Zapf, Ludwig and Friedrich, Alexandra and Ignat'ev, Nikolai V. and Finze, Maik and Radius, Udo},
  title     = {Tris(pentafluoroethyl)difluorophosphorane: a versatile fluoride acceptor for transition metal chemistry},
  series = {Chemistry Europe},
  volume    = {27},
  journal   = {Chemistry Europe},
  number    = {10},
  doi       = {10.1002/chem.202004885},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256665},
  pages     = {3504-3516},
  year      = {2021},
  abstract  = {Fluoride abstraction from different types of transition metal fluoride complexes [L\(_n\)MF] (M=Ti, Ni, Cu) by the Lewis acid tris(pentafluoroethyl)difluorophosphorane (C\(_2\)F\(_5\))\(_3\)PF\(_2\) to yield cationic transition metal complexes with the tris(pentafluoroethyl)trifluorophosphate counterion (FAP anion, [(C\(_2\)F\(_5\))\(_3\)PF\(_3\)]\(^-\)) is reported. (C\(_2\)F\(_5\))\(_3\)PF\(_2\) reacted with trans-[Ni(iPr\(_2\)Im)\(_2\)(Ar\(^F\))F] (iPr2Im=1,3-diisopropylimidazolin-2-ylidene; Ar\(^F\)=C\(_6\)F\(_5\), 1 a; 4-CF\(_3\)-C\(_6\)F\(_4\), 1 b; 4-C\(_6\)F\(_5\)-C\(_6\)F\(_4\), 1 c) through fluoride transfer to form the complex salts trans-[Ni(iPr\(_2\)Im)\(_2\)(solv)(Ar\(^F\))]FAP (2 a-c[solv]; solv=Et\(_2\)O, CH\(_2\)Cl\(_2\), THF) depending on the reaction medium. In the presence of stronger Lewis bases such as carbenes or PPh\(_3\), solvent coordination was suppressed and the complexes trans-[Ni(iPr\(_2\)Im)\(_2\)(PPh\(_3\))(C\(_6\)F\(_5\))]FAP (trans-2 a[PPh\(_3\)]) and cis-[Ni(iPr\(_2\)Im)\(_2\)(Dipp\(_2\)Im)(C\(_6\)F\(_5\))]FAP (cis-2 a[Dipp\(_2\)Im]) (Dipp\(_2\)Im=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were isolated. Fluoride abstraction from [(Dipp\(_2\)Im)CuF] (3) in CH\(_2\)Cl\(_2\) or 1,2-difluorobenzene led to the isolation of [{(Dipp\(_2\)Im)Cu}\(_2\)]\(^2\)\(^+\)2 FAP\(^-\) (4). Subsequent reaction of 4 with PPh\(_3\) and different carbenes resulted in the complexes [(Dipp\(_2\)Im)Cu(LB)]FAP (5 a-e, LB=Lewis base). In the presence of C6Me6, fluoride transfer afforded [(Dipp\(_2\)Im)Cu(C\(_6\)Me\(_6\))]FAP (5 f), which serves as a source of [(Dipp\(_2\)Im)Cu)]\(^+\). Fluoride abstraction of [Cp\(_2\)TiF\(_2\)] (7) resulted in the formation of dinuclear [FCp\(_2\)Ti(μ-F)TiCp\(_2\)F]FAP (8) (Cp=η\(^5\)-C\(_5\)H\(_5\)) with one terminal fluoride ligand at each titanium atom and an additional bridging fluoride ligand.},
  language  = {en}
}